Endoscopic surgery is less invasive to a patient in comparison with general surgery and has been recently popular. In the endoscopic surgery, an operator or the like checks an affected area using images, and hence it is sometimes difficult to stereoscopically grasp the affected area using conventional two-dimensional images. In view of this, for example, a head-mounted display (HMD) capable of providing three-dimensional images is connected to an endoscopic apparatus and used such that more precise and speedy endoscopic surgery can be performed while viewing realistic images of the affected area with a stereoscopic effect (see Patent Document 1).
By the way, during endoscopic surgery, the operator or the like may refer to other diagnosis images such as an ultrasonic image as well as endoscopic images. Thus, when using the HMD for endoscopic surgery, there is a need for providing a configuration in which the operator or the like can view not only the endoscopic images displayed on the HMD but also the other diagnosis images displayed on an external monitor or the like. In view of this, for example, Patent Documents 2 and 3 each describe an HMD whose display is placed in only a part of a field of view such that an outside can be seen through a region other than the display. In addition, Patent Document 4 describes an HMD that ensures that an outside can be seen by rotating a mirror or the like that displays images to left and right eyes.
Patent Document 1: Japanese Patent Application Laid-open No. 2011-145488
Patent Document 2: Japanese Patent Application Laid-open No. 2000-060876
Patent Document 3: Japanese Patent Application Laid-open No. HEI 8-206083
Patent Document 4: Japanese Patent Application Laid-open No. 2011-112828